Question

I’m having trouble understanding CommandName and CommandArgument associated with an ASP.NET LinkButton. I have read this article – http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.button.commandname.aspx and other questions on this site.

I guess my questions are – what exactly is a “Command”? Can a CommandName basically be any text? I see “Sort” and “Submit” as examples. And as for CommandArgument, this is just used to further specify the type of “Command”. Correct?
Thanks very much for your help.

Answer 1

A Command can be anything you want it to be.

The basic idea is that if you say have a repeater, and in that repeater you have multiple options, you can give each option a different CommandName. The CommandArgument would then be based on the unique identifier of the line.

Then on the post-back you can check which CommandName was fired and based on that use the value in the CommandArgument

For Example, the mark-up could look something like…

<asp:Repeater runat="server" id="myRepeater">
  <ItemTemplate>
    <div>
      <asp:LinkButton runat="server" id="lnkEdit" CommandName="edit" 
        CommandArgument="<%#Container.DataItem.Id%>" Text="Edit" 
        OnClick="OnClickHandler" />
      <asp:LinkButton runat="server" id="lnkDelete" CommandName="delete" 
        CommandArgument="<%#Container.DataItem.Id%>" Text="Delete"
        OnClick="OnClickHandler" />
    </div>
  </ItemTemplate>
</asp:Repeater>

Then your post-pack handler could check to see which one was clicked…

Protected Sub OnClickHandler(ByVal sender As Object, ByVal e As EventArgs)
  Dim lnk as LinkButton = CType(sender,LinkButton)
  Select Case lnk.CommandName
    Case "edit"
      EditItem(lnk.CommandArgument)
    Case "delete"
      DeleteItem(lnk.CommandArgument)
  End Select
End Sub